Study Design: Computational analyses using optimization finite element (FE) models. Objective: To determine the spinal muscle forces (MFs) creating compressive follower loads (CFL) in the lumbar spine in various sagittal postures and to investigate if such MFs can maintain the spinal stability. Summary of Background Data: Biomechanical loads are known closely associated with spinal disorders. Normal spinal loads, however, remains poorly understood due to the lack of knowledge of the MF control mechanism for normal biomechanical functions. Methods: 3-D optimization and FE models of the spinal system (trunk, lumbar spine, sacrum, pelvis, and 232 muscles) were developed and validated using reported experimental data. Optimization models were used to determine the MFs creating CFLs in the lumbar spine in various sagittal postures from 10 extension to 40 flexion. The deformation of the lumbar spine under these MFs and trunk weight was predicted from FE models. The stable lumbar spine deformation was determined by the resultant trunk sway < 10 mm. Results: Optimization solutions of MFs, CFLs, and follower load path (FLP) location were feasible for all studied postures. The FE predictions clearly demonstrated that MFs creating CFLs along the base spinal curve connecting the geometrical centers or along a curve in its vicinity (within anterior or posterior shift by 2 mm) produce the stable deformation of the lumbar spine in the neutral standing and flexed postures, whereas the MFs creating the smallest CFLs resulted in the unstable deformation. In case of extended postures, however, it was not possible to find the CFL creating MFs that produce stable deformation of the extended spine. Conclusion: The results of this study demonstrated the feasibility for spinal muscles to stabilize the spine via the CFL mechanism.

Back injury in nursing is a significant concern for the health of the worker, the costs to the healthcare system, and the safety of the patients. Current injury prevention measures include ergonomic adjustments to the work environment, the use of mechanical lifting equipment, policies to limit manual handling of patients, and the teaching of lifting techniques. These measures have been met with limited success in reducing injury rates. Little is known about whether changing the lifting biomechanics used in the healthcare setting can lower high injury rates across the profession. The purposes of this dissertation were to: 1) identify the biomechanical risk factors routinely encountered by healthcare workers during the performance of their daily job tasks and 2) determine whether nurses with formal training in weightlifting have better biomechanical performance during routine nursing tasks than nurses with no training. This dissertation included the development of a conceptual model to guide the research. The framework identified the impact of muscle fatigue on the biomechanics used in lifting and moving of heavy equipment and patients. The worker characteristics that affect muscle fatigue include age, gender, height, BMI and the type of recreational activities outside of the workplace. These characteristics were controlled for in two studies aimed at providing a greater understanding of biomechanics used by nurses during routine patient care related activities. The first study addressed a gap in knowledge related to the biomechanics of lifting techniques used by nurses in the work environment, specifically of the anterior rotation of the trunk and pelvis, angles of the hips, knees, and lumbar spine, and muscle activation of core and leg muscles used during patient care activities. We analyzed the biomechanics used by 11 senior level nursing students lifting a simulated patient attached to a rigid spine board from the floor to a standing height. Previous studies have identified that a lumbar spine angle in excess of 22.5 degrees flexion when performing a lift places a worker at a greater risk for back injury. Biomechanical risk factors effecting this lumbar spine angle identified in this study included the anterior rotation of the trunk and pelvis in the starting position of the lift, the angle of the hips and knees during the lifting cycle, the dominate muscle activation of the rectus femoris during the lifting cycle influencing the anterior pelvic rotation, and minimal activation of the core muscles required to add stability to the spine during the lift. This dissertation identifies common biomechanical risk factors routinely encountered by healthcare workers, and gives indication of differences between nurses with formal weightlifting training and those that have not received formal weightlifting training. The differences in body positioning and core stabilization can help reduce the biomechanical risks of back injury in nursing.

This aim of this study was to answer the research question: "What is the Life Pattern of the Person with Spinal Cord Injury?" The unitary appreciative inquiry design, which has conceptualized through Rogers' (1986) science of unitary human beings, provided an approach for understanding the phenomenon in the context of human wholeness. The data, obtained through the methodology of unitary appreciative inquiry, led to the development of individual synopses for each of the participants. Once the synopses were completed, a composite pattern profile was constructed by the researcher that was indicative of the life pattern of people with spinal cord injury. The participants in the study validated the synopsis and pattern profile as accurate representations of their experience with spinal cord injury. This qualitative study, which was comprised of eight people who had undergone a spinal cord injury more than two years prior to the study, discovered three shared pattern manifestations: depersonalization; loss; and hopelessness. Although each person within this inquiry had a very good physical outcome concerning their spinal cord injury, the participants were not pleased with their current state of being. The pattern of despair, which was validated by the participants, was manifested through the profound sense of depersonalization, loss, and hopelessness.

No description available.

Cervical myelopathy is the most common form of spinal cord injury in North America with roughly 19,000 new cases in the US every year. It results from chronic compression of the spinal cord by osteophytes, intervertebral disc herniation, and ossified ligaments. It commonly affects adults over the age of 50 years and causes upper extremity numbness, loss of hand dexterity, gait disturbances, and decreased proprioception. Recent studies imaging studies have shown this injury is highly dependent on the dynamic motion of the spine, often worsening in extreme flexion and extension. Surgical intervention is the accepted mode of treatment with the aim of decompressing the spinal canal and stabilizing the spine. However, 25% of patients have reoccurrence of symptoms indicating that surgical treatments may not be adequately addressing the injury. A main reason for this is little data has been reported on the spinal cord mechanics during cervical spinal motion in either healthy or cervical myelopathy subjects. To address this, we utilized MR imaging and finite element modeling to investigate spinal cord mechanics. As far as we know, we are the first group to obtain in vivo 3 dimensional spinal cord displacement and strain data from human subjects and the first to develop a C2 to T1 FE model of the healthy and cervical myelopathic spine and spinal cord. Utilizing high resolution 3T MR imaging in neutral, flexion, and extension positions we were able to obtain spinal cord displacement and strain fields from both healthy subjects and cervical myelopathy subjects before and after surgical intervention. In healthy subjects, flexion motion of the spine causes the spinal cord to move superiorly and in extension the spinal cord moves inferiorly. During extension, localizations of high principal strain can be seen in healthy subjects at areas of bony impingement and dural buckling. In both flexion and extension, cervical myelopathy subjects exhibited very little spinal cord displacement due to spinal cord compression. Principal strains during flexion and extension were greater in cervical myelopathy patients than healthy patients, specifically at the C4-6 vertebral levels. Surgical treatments for cervical myelopathy did restore spinal cord motion however, not in the same pattern or direction as healthy subjects. Additionally principal strains of the spinal cord were not reduced after surgical intervention. This indicates that surgical interventions are not adequately addressing the altered mechanics of the spinal cord during cervical myelopathy. To determine the how common surgical techniques for cervical myelopathy affect spinal cord mechanics, a FE model of the cervical spine and spinal cord was developed. The spinal cord motion was validated against MR imaging data obtained from normal subjects. Once validated, the model was used to develop a FE model of cervical myelopathy and surgical interventions. The native FE model predicted spinal cord motion well and replicated bony spinal cord impingement and dural buckling seen in healthy subjects. The FE model of cervical myelopathy also replicated spinal cord motion well as compared to MR imaging data of cervical myelopathy. Principal strains obtained from the healthy and cervical myelopathy FE models were similar in flexion however in extension, principal strains were higher at the C3, C6 and C7 levels. This is different than the patterns exhibited in the MR imaging and is most likely due to the percent of spinal cord compression induced in the FE model. Three, C4 to C7 surgical interventions were introduced to the model: anterior discectomy and fusion, anterior discectomy and fusion with laminectomy, and double door laminoplasty. In flexion, all surgical treatments doubled spinal cord principal strains at the C3 level and minimally reduced tensile strain at C4. The majority of strain reduction occurred at C5-7. In extension, all surgical techniques increased principal strains at the C3 and C4 levels. Little or no reduction in principal strains was seen at the C5 and C7 levels. All surgical techniques reduced principal strains at the C6 level. Of the surgical techniques, ACDF tended to reduce spinal cord principal strains the least in both flexion and extension and tended to induce the highest von Mises stresses. Combining the data obtained from MR imaging and FE modeling we can see that cervical myelopathy alters spinal cord mechanics by limiting spinal cord motion and increasing spinal cord strain. Additionally, current surgical techniques are not addressing the change in spinal cord mechanics effectively. Specifically after surgery, and especially with ACDF, spinal cord displacements and strains are being increased and transferred to different sections of the spinal cord. This indicates not only the need and importance of further research in spinal cord mechanics but also the need to improve treatments for cervical myelopathy which adequately restore the spinal cord mechanics.

The cause and best treatment option for mechanical low back pain due to disc degeneration remains unsolved, despite `spinal fusion' being the gold standard of surgical treatment, post conservative care, for a very long time. However, the potential drawbacks of spinal fusion and the ongoing evolution in the understanding of normal and symptomatic spine biomechanics, biology and mechanobiology in conjunction with the advancements in material sciences, and tissue engineering has led to a change in the clinical perspective towards treatment methodologies for spinal disorders. Clinically, a gradual shift in philosophy is being observed from a `one size fits all', i.e. spinal fusion for all patients with symptomatic low back pain to a `customized approach', i.e. patient and indication specific treatment modalities for spine care. This philosophy has laid the ground for concepts of `motion preservation' and `dynamic stabilization', the former being an established treatment modality in orthopedics for a long time. The aim of the current study is to perform a comprehensive scientific investigation to understand, evaluate and establish the in vitro biomechanical characteristics and performance of indication specific treatment modalities incorporating the concept of Posterolateral Disc Arthroplasty and Posterior Dynamic Stabilization for the treatment of symptomatic mechanical back pain. The results of this comprehensive study may help the clinicians to make an informed decision while selecting and designing a treating modality for their patients. To this end, the current thesis was undertaken to study the biomechanics of indication specific treatment modalities like motion preservation and dynamic stabilization with a goal to guide clinical and product development decision making. Through the comprehensive biomechanical investigation conducted in the current thesis we were able to theoretically prove the importance of a customized approach towards the treatment of spine care. Also, the most important conclusion of the biomechanical investigation was the fact that Range of Motion results alone are not sufficient to draw significant conclusions. It is imperative that in depth analysis of the quality of motion through the determination of instantaneous center of rotation is extremely important. Previous studies have shown only a single center of rotation between the extremes of motion which is also insufficient as the end points do not determine the path taken to reach the endpoints. This in depth analysis is also important for biomedical engineers to design and develop physiologically viable implants that will mimic the performance of the physiologic spine. Clinical studies are extremely important as a next step towards validating this customized approach towards spine care.

Previous in-vivo studies showed that compressive force acting on the spine may exceed 2600 N. However, the ligamentous lumbar spine becomes unstable when subjected to compressive loads less than 100 N. It is generally accepted that the ligamentous spine itself is unstable but can be stabilized by muscle forces (MFs) in vivo. Nevertheless, normal spinal muscle contraction patterns remain unknown. In recent in vitro studies, when the direction of the applied load was controlled along the spinal curvature so that the internal spinal load became perfect compressive follower loads (CFLs) at all lumbar levels, the ligamentous lumbar spine was found to withstand large compressive load (up to 1200 N) without buckling while maintaining its flexibility in neutral or flexed postures. The results of in-vivo animal studies also have shown that shear stress has a more detrimental effect on the rate of disc degeneration compared to compressive stress. These results suggest CFLs in the lumbar spine would be a normal spinal load whereas the transverse (or shear) load abnormal. An initial test of this postulation would be to investigate whether the spinal muscles can create perfect internal CFLs in the lumbar spine in all 3-D postures. In addition, small intrinsic muscles (SIMs) are crucial for better control of the direction of the internal spinal load along the spinal axis was also proposed. A finite element (FE) model together with an optimization model were used for this study. Both models consist of the trunk, sacrolumbar spine and 244 spinal muscles. Different from other studies, 54 SIMs were also included in the models. The FE model was validated by comparing the ROM of the spine with the literature data. Minimization of the summation of the spinal loads and moments was used as the cost function for the optimization model. The geometrical data obtained from the FE model was used as the input for the optimization model; it was then used to calculate the MFs required for creating the CFLs at all lumbar spine levels. The MFs determined in the optimization model were then imported back to the FE model as input loads to check the stability of the spine under this loading condition. Five different postures were studied: neutral, flexion 40°, extension 5°, lateral bending 30° and axial rotation 10°. Many optimization solutions for spinal muscle force combinations creating pure CFLs in the lumbar spine were found available in each posture. However, FE analyses showed that only muscle forces and patterns solved at FLPs along the curve in the vicinity of the baseline curve stabilized the lumbar spine. Stability was determined by small displacement of the trunk (less or equal to 5mm) due to small deformation of the lumbar spine. The magnitudes of joint reaction forces (JRFs) predicted from the optimization model were comparable to those reported in the literature. When the SIMs were removed, optimization solutions were still feasible in all five postures, but JRFs and trunk displacement were increased. This suggests the need of SIM inclusion in future spine biomechanics studies and clinically, damages to the SIMs may have a high risk of future spinal problems, such as spinal instability, early disc degeneration, deformity and/or early failure of spinal fixation devices. The results from this study supported the hypothesis that the perfect CFLs at all lumbar levels could be the normal physiological load under which the lumbar spinal column could support large load without buckling while allowing flexibility. SIMs played an important role in creating CFLs as by including SIMs in the models, the JRFs at all lumbar spine levels were lowered and the stability of the spine was increased.

Cervical spondylotic myelopathy is the most common spinal cord disorder in persons over 55 years of age in North America and perhaps in the world. Surgical options are broadly classified into two categories namely, anterior and posterior approaches. This study focuses on the posterior based approach (i.e. laminectomy or laminoplasty) which is considered when multiple levels of the spine have to be decompressed or when most of the cord compression results from posterior pathological conditions. The external and internal behavior of the spine after laminoplasty and laminectomy has been evaluated using both experimental and computational methods. Computationally, a validated intact 3D finite element model of the cervical spine (C2-T1) was modified to simulate laminectomy and laminoplasty (open door (ODL) and double door (DDL)) at levels C3-C6. During flexion, after ODL the adjacent levels C2-C3 and C6-C7 showed a 39% and 20% increase in the motion respectively; while no substantial changes were observed at the surgically altered levels. The percent increase in motion after DDL varied from 4.3% to 34.6%. The inclination towards increased motion during flexion after double door laminoplasty explains the role of the lamina-ligamentum flavum complex in the stability of spine. Compared to the intact model, laminectomy at C3-C6 led to a profound increase (37.5% to 79.6%) in motion across the levels C2-C3 to C6-C7. Furthermore, the changes in the von Mises stresses of the intervertebral disc observed after laminoplasty and laminectomy during flexion can be correlated to the changes in the intersegmental motions. An in-vitro biomechanical study was conducted to address the effects of laminoplasty (two-level and four-level) and four-level laminectomy on the flexibility of the cervical spine. Both two-level and four-level laminoplasty resulted in minimal changes in C2-T1 range of motion. For flexion/extension, two-level and multi-level laminoplasty showed an approximate 20% decrease (p>0.05) in the range of motion at C4-C5 and C2-C3 respectively due to the encroachment of the spinous process into the opened lamina. The decrease was mostly observed in older specimens and specimens with adjacent laminae close to each other; thus leading to the encroachment of the spinous process into the opened lamina. Laminectomy resulted in a statistically significant (p<0.05) increase in the range of motion compared to the intact condition during the three loading modes. These results correspond well with the finite element predictions, where a four-level ODL and laminectomy resulted in a minimal 5.4% and a substantial 57.5% increase in C2-T1 motion respectively during flexion. Adaptive bone remodeling theory was applied to the open door laminoplasty model to understand the effect of the surgical procedure on the internal architecture of bone. Bone remodeling was implemented at the C5 vertebra by quantifying the changes in apparent bone density in terms of the mechanical stimulus (i.e. SED/density). After laminoplasty, the increased load distribution through the bony hinge region led to the increased bone density during extension. This increased bone density could eventually lead to bone formation in those regions through external remodeling. The current study proved laminoplasty to be a motion preservation technique wherein the plates and spacer provided additional stability via reconstruction of the laminar arch while laminectomy can cause instability of spine especially during flexion. In the future, patient-specific finite element models that incorporate geometry-related differences could be developed to optimize the number of operated levels and to further explain the effect of surgical procedure on the unaltered levels.

Radiofrequency neurotomy is a pain intervention procedure designed to coagulate nerves that innervate a specific area of spinal vertebrae known as the facet joint. Despite moderate to strong research support for the efficacy of radiofrequency neurotomy to improve short-term subjective pain levels, much of the literature to date has used strict selection criteria and has not focused on functional and quality of life outcomes. Moreover, few studies have examined outcomes in worker's compensation patients or considered biopsychosocial predictive variables for the procedure. The current study aimed to characterize injured workers who have undergone radiofrequency neurotomy across a number of pre and post-procedural variables, evaluate multidimensional functional and quality of life outcomes, and examine biopsychosocial variables predictive of success and failure in this sample. The current study comprised 101 injured workers who had undergone at least one radiofrequency neurotomy of the spine (cervical, thoracic, or lumbar) in the past 11 years. Participants were solicited through the Worker's Compensation Fund of Utah computerized database. Employing a retrospective cohort design, patients' medical charts were reviewed and various preprocedural variables were coded for analysis including age at the time of the first neurotomy, history of depression, lawyer involvement in the claim, prior back and neck surgical history, and quantity of other compensation claims. Of the total sample, 56 patients (55.4%) were contacted and completed outcome surveys that assessed patient satisfaction, functional impairment, disability status, pain catastrophization, and general physical and mental health functioning. Findings revealed a moderate proportion of patients with total disability (40%), poor back/neck specific functioning (63%), and dissatisfaction with their current back/neck condition (75%). A multivariate regression model was consistently predictive of patient outcomes. Specifically, litigation status was a robust predictor of multidimensional outcomes, while depression and age retained slightly less predictive power. Results of descriptive, correlational, and regression analyses are compared to existing data for radiofrequency neurotomy and other spine procedures with similar populations. Limitations of the study are discussed, such as the retrospective design, lack of matched controls, and small sample size.

Introduction. To test the effects of torsion torques on intradiscal pressure and disc height in human lumbar specimens. Methods. Six human lumbar cadaveric functional spine units (FSU) were loaded in the neutral position with 600 N compression. Nucleus pressure measurements were obtained at 0 Nm, 0.5 Nm, 1.0 Nm and 2 Nm torsion torque. Posterior elements were removed and pressure measurements were repeated at the same torsion torques for the disc body unit (DBU). The pressure in the nucleus was measured by pulling a pressure probe through the disc along a straight path in the midsagittal plane. Results. There was no statistically significant difference of nucleus pressure or intervertebral disc height with different torsion torques among or between the FSU's and DBU's. However, a disc height increase ranging from 0.13 mm to 0.16 mm occurred with the insertion of a 1.85 mm diameter cannula. Conclusions. Small torsion torques showed no significant difference in intradiscal pressures or disc heights. Disc height increases were seen with the insertion of the cannula that could lead to methods of disc height restoration.